Modular scaffolding systems may comprise a limited number of different building elements that can be connected together in large numbers to form a variety of scaffold frames that can be tailored to specific sites and applications. A modular scaffold frame may typically comprise a plurality of standards (also called uprights), ledgers and cross-braces. The standards are connected to form vertically extending columns that are spaced apart at regular intervals. Horizontally oriented ledgers interconnect the columns at different height levels to form a more or less regular framework. Points where ledgers connect to standards are called nodes. The cross-braces may diagonally interconnect these nodes, either connecting nodes of the same height level or connecting nodes of different levels, in order to increase the rigidity of the scaffold frame.
Individual ledgers of a scaffolding system may be connected to individual standards through a coupling construction. Known coupling constructions have a number of drawbacks that inhibit the quick erection of a scaffold frame.
U.S. Pat. No. 4,044,523, for example, discloses a scaffold frame including a plurality of tubular standards of circular cross-section, each standard including a number of axially spaced ring flanges. The ring flanges are concentric with the respective standards and are each formed with circumferentially distributed cut-outs of different shapes. A plurality of ledgers interconnect the respective standards. Each ledger has two end portions or couplings, while each coupling is formed with an axial slot having a width at least equal to the thickness of the respective ring flanges, and subdividing the respective coupling into two sections provided with registering openings extending normal to the elongation of the respective ledger. A releasable wedge member extends through these openings across the slot and through one of the cut-outs of a ring flange which is in part located in the slot.
In the scaffolding system of U.S. Pat. No. '523, a coupling construction involves a ring flange (connected to a standard), a coupling (connected to an extremity of a ledger), and a wedge member. Assembling a scaffold frame with such coupling constructions may repeatedly require a scaffolding builder to mount a ledger between two standards. While balancing the ledger between the standards, he has to insert a portion of the respective ring flanges provided thereon into the slots in the respective couplings at the extremities of the ledger. Once he has succeeded in doing so, he may turn to either coupling and bring the openings in the respective coupling into alignment with one of the various cut-outs in the respective ring flange. To achieve alignment he may have to jiggle the respective extremity of the ledger, which may also cause the opposite extremity, which is still loosely supported on the respective ring flange, to shift and fall off. Only when he has carefully selected the desired cut-out, and moved the coupling openings into alignment therewith, he may insert a wedge member trough the aligned cut-out and openings to lock the respective ledger end to the standard.
It will be appreciated that the acts of initially placing the ledger between two standards so that it is loosely supported on two ring flanges, and of jiggling the ledger to select the desired cut-out and to bring the openings in the coupling in registry therewith, while at the same time preventing the opposite end of the ledger from shifting and falling, are relatively time consuming and require skill on the part of the scaffold builder. In addition, falling ledgers may injure the scaffold builder, which renders the ledgers unsafe in use.
It is an object of the present invention to overcome or mitigate one or more of these drawbacks associated with known scaffolding systems, and to provide for a coupling construction that facilitates the task of quickly and safely erecting a scaffold frame.